32 Questions
average plasma glucose
298 mg/dL (16.5 mmol/L) = 12 269 mg/dL (14.9 mmol/L) = 11 240 mg/dL (13.4 mmol/L) = 10 212 mg/dL (11.8 mmol/L) = 9
average plasma glucose
183 mg/dL (10.2 mmol/L) = 8 154 mg/dL (8.6 mmol/L) = 7 97 mg/dL (5.4 mmol/L) = 5 126 mg/dL (7.0 mmol/L) = 6
What is the result of glucose reacting with the amino group of Hemoglobin?
Formation of a ketoanime
What is the normal range of HbA1c values?
4-6%
How long are HbA1c samples stable for?
1 week
What is the formula used to calculate average glucose from HbA1c results?
𝑒𝐴𝐺 (𝑚𝑔/𝑑𝐿) = 28. 7 × 𝐻𝑏𝐴1𝑐 − 46. 7
Why is it recommended to test glucose levels in the morning?
Due to the diurnal variation of glucose concentration
What is the recommended duration of fasting before measuring glucose levels?
8-10 hours
NELSON SOMOGYI = Copper reduction methods Glucose is a reducing agent of copper. Glucose + arsenomolybdic acid = arsenomolybdenum blue Clinitest tablet = Copper reduction HAGEDORN JENSEN = Ferric reduction method Glucose is a reducing agent of iron. Glucose + Ferricyanide (yellow) = ferrouscyanide (colorless) ORTHO-TOLUIDINE (DUBOWSKI) = Condensation with aromatic amines to Schiff bases (green color)
What is the principle of affinity chromatography measurement of HbA1c?
Glycosylated hemoglobin attaches to the resin and is selectively eluted using a buffer
What is an advantage of affinity chromatography measurement of HbA1c?
It is not affected by hemoglobin F, S, or C
What is the role of the boronate group in affinity chromatography measurement of HbA1c?
It attaches to the glycosylated hemoglobin and selectively retains it on the resin
What is a characteristic of the affinity chromatography method of HbA1c measurement?
It is not affected by temperature
What is the reactant used in Gerhardt's method to produce a red color?
Ferric chloride
What is the pH condition required for the reaction in the sodium nitroprusside method?
Alkaline
Which method detects either 3-b-hydroxybutyric acid or acetoacetic acid?
Enzymatic method
What is the enzyme used in the enzymatic method?
3-hydroxybutyrate dehydrogenase
What type of sample can be used for ketone detection?
Either serum or urine
ketone test
Sodium nitroprusside = acetoacetic acid / Purple Enzymatic = dehydrogenase - 3-b-hydroxybutyric acid or acetoacetic acid Gerhardt’s = ferric chloride acetoacetic acid / red color 123 = 123
What is the earliest sign of nephropathy before the development of creatinuria?
Microalbuminuria
How many specimens are required to confirm microalbuminuria?
2-3 specimens
What is measured to confirm microalbuminuria?
Albumin-creatinine ratio
What is the purpose of testing for microalbuminuria?
To identify early signs of nephropathy
What is the timeframe for collecting specimens to confirm microalbuminuria?
3-6 months
what is a part of Albumin-creatinine ratio
all of the above
Urine glucose measurement is not used
True
sample used for HbA1c should be plasma
False
What is microalbuminuria defined as?
Persistent albuminuria in two out of three urine collections of 30 to 300 mg/24 h
What is clinical proteinuria or macroalbuminuria established with?
An albumin-creatinine ratio ≥300 µg/mg
What can increase urine albumin?
All of the above
What is the unit of measurement not for microalbuminuria in terms of albumin excretion rate?
mg/min
What is the timeframe in which exercise can increase urine albumin?
Within 24 hours
Study Notes
HbA1c Formation
- Glucose reacts with the amino group of Hemoglobin (Hb A1) to form a ketoamine.
- This reaction occurs non-enzymatically, attaching glucose to the Hb molecule.
HbA1c Normal Values and Sample Stability
- Normal HbA1c values range from 4-6%.
- No fasting is required for patients before taking HbA1c samples.
- Samples are stable for up to 1 week.
Calculating Average Glucose from HbA1c
- Average glucose can be calculated using the HbA1c result and the formula: 𝑒𝐴𝐺 (𝑚𝑔/𝑑𝐿) = 28.7 × 𝐻𝑏𝐴1𝑐 − 46.7
HbA1c Formation
- Glucose reacts with the amino group of Hemoglobin (Hb A1) to form a ketoamine.
- This reaction occurs non-enzymatically, attaching glucose to the Hb molecule.
HbA1c Normal Values and Sample Stability
- Normal HbA1c values range from 4-6%.
- No fasting is required for patients before taking HbA1c samples.
- Samples are stable for up to 1 week.
Calculating Average Glucose from HbA1c
- Average glucose can be calculated using the HbA1c result and the formula: 𝑒𝐴𝐺 (𝑚𝑔/𝑑𝐿) = 28.7 × 𝐻𝑏𝐴1𝑐 − 46.7
Glucose Measurement
- Glucose concentration can be measured in serum, plasma, or whole blood
- Whole blood glucose concentration is approximately lower than in plasma
- Fasting Plasma Glucose (FPG) levels are higher in the morning compared to the afternoon and night due to diurnal variation
- FPG testing should be conducted in the morning to account for this variation
- Patients must fast for 8-10 hours (not exceeding 16 hours) prior to testing
- It is essential to ask the patient about the exact time of their last meal before testing
- Urine glucose measurement is not a reliable method and is not used
Copper Reduction Methods
- Glucose acts as a reducing agent for copper
- Reaction of glucose with arsenomolybdic acid produces arsenomolybdenum blue
- This reaction is utilized in Clinitest tablets for glucose detection
Iron Reduction Methods
- Glucose acts as a reducing agent for iron
- Reaction of glucose with ferricyanide (yellow) produces ferrocyanide (colorless)
- This method is known as the Ferric reduction method (Hagedorn-Jensen method)
Ortho-Toluidine Method (Dubowski Method)
- Glucose reacts with aromatic amines to form Schiff bases, resulting in a green color
- This reaction is used for glucose detection
Affinity Chromatography HbA1c Measurement Preferred method of measurement The glycosylated hemoglobin (A1c) attaches to the boronate group of the resin and is selectively eluted from the resin bed using a buffer. This method is not temperature dependent. Not affected by hemoglobin F, S, or C.
Affinity Chromatography HbA1c Measurement Preferred method of measurement The glycosylated hemoglobin (A1c) attaches to the boronate group of the resin and is selectively eluted from the resin bed using a buffer. This method is not temperature dependent. Not affected by hemoglobin F, S, or C.
Sample Types for Ketone Detection
- Samples can be either serum or urine for ketone detection.
Gerhardt's Method
- Uses ferric chloride reacted with acetoacetic acid to produce a red color.
- Ferric chloride is the key reactant in this method.
Sodium Nitroprusside Method
- Reacts with acetoacetic acid in an alkaline pH to form a purple color.
- Alkaline pH is a necessary condition for this method to work.
Enzymatic Method
- Uses 3-hydroxybutyrate dehydrogenase to detect either 3-b-hydroxybutyric acid or acetoacetic acid.
- 3-hydroxybutyrate dehydrogenase is the enzyme involved in this method.
Microalbuminuria and Kidney Damage
- High glucose levels can damage kidneys, but before that, patients experience microalbuminuria, characterized by an increased albumin-creatinine ratio.
- To diagnose microalbuminuria, 2-3 urine specimens are collected within a 3-6 month period, and if all are abnormal, the patient is considered to have microalbuminuria.
- Microalbuminuria is a crucial early sign of nephropathy, preceding the development of creatinuria.
- There are three methods to measure albumin-creatinine ratio:
Methods for Albumin-Creatinine Ratio Measurement
- Random Spot Collection
- 24-Hour Collection
- Timed 4-Hour Overnight Collection
Factors Affecting Urine Albumin
- Exercise within 24 hours can increase urine albumin
- Infection can increase urine albumin
- Fever can increase urine albumin
- CHF (Congestive Heart Failure) can increase urine albumin
- Marked hyperglycemia can increase urine albumin
- Marked hypertension can increase urine albumin
Microalbuminuria
- Defined as persistent albuminuria in two out of three urine collections
- Characterized by: • 30-300 mg/24 h urine albumin excretion • 20-200 µg/min urine albumin excretion rate • Albumin-creatinine ratio of 30-300 µg/mg creatinine
Clinical Proteinuria/Macroalbuminuria
- Established with: • Albumin-creatinine ratio ≥300 mg/24 h • Urine albumin excretion rate >200 µg/min • Albumin-creatinine ratio ≥300 µg/mg
Learn about the HbA1c lab test, which measures average glucose levels in the blood. Understand how it works, normal values, and how to calculate average glucose levels from the test result.
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